Methods of fabricating three-dimensional semiconductor devices

ABSTRACT

A three-dimensional semiconductor device includes an upper structure on a lower structure, the upper structure including conductive patterns, a semiconductor pattern connected to the lower structure through the upper structure, and an insulating spacer between the semiconductor pattern and the upper structure, a bottom surface of the insulating spacer being positioned at a vertical level equivalent to or higher than an uppermost surface of the lower structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional application based on pending application Ser. No.13/290,425, filed Nov. 7, 2011, the entire contents of which is herebyincorporated by reference.

This U.S. non-provisional patent application claims priority under 35U.S.C. §119 to Korean Patent Application No. 10-2010-0110033, filed onNov. 5, 2010, in the Korean Intellectual Property Office, the entirecontents of which are hereby incorporated by reference.

BACKGROUND

1. Field

Example embodiments of the inventive concepts relate to semiconductordevices and methods of fabricating the same, and more particularly, tothree-dimensional semiconductor memory devices includingthree-dimensionally arranged memory cells and methods of fabricating thesame.

2. Description of the Related Art

A three dimensional integrated circuit (3D-IC) memory technique may beused for increasing a memory capacity. 3D-IC memory technique refersgenerally to technologies related to arranging memory cellsthree-dimensionally. In addition to a 3D-IC memory technique, a memorycapacity may be increased through (1) a pattern miniaturizationtechnique, and (2) a multi-level cell (MLC) technique. However, the useof a pattern miniaturization technique may be limited due to high cost,and the capacity increase achieved by the MLC technique may be limitedto the number of bits to be increased in each cell. The patternminiaturization technique and the MLC techniques may be combined withthe 3D-IC technique, in terms of realizing a more increased memorycapacity, and may be expected to develop separately from the 3D-ICtechnique.

One 3D-IC technique is a punch-and-plug technique. The punch-and-plugtechnique includes sequentially forming multi-layered thin layers on asubstrate and then forming plugs to penetrate the thin layers. Throughthis technique, without a drastic increase of manufacturing costs, amemory capacity of a three-dimensional memory device may be achieved.

SUMMARY

Embodiments of the inventive concepts provide three-dimensionalsemiconductor devices configured to reduce electric resistance of anelectric current path therein.

Other embodiments of the inventive concepts provide methods offabricating a three-dimensional semiconductor device configured toreduce electric resistance of an electric current path therein.

According to example embodiments of the inventive concepts, athree-dimensional semiconductor device may include an upper structure ona lower structure, the upper structure including conductive patterns, asemiconductor pattern connected to the lower structure through the upperstructure, and an insulating spacer between the semiconductor patternand the upper structure, a bottom surface of the insulating spacer beingpositioned at a vertical level equivalent to or higher than an uppermostsurface of the lower structure.

The lower structure may include a semiconductor substrate, thesemiconductor pattern being directly connected to the semiconductorsubstrate.

The semiconductor substrate may include a doped region spaced apart fromthe semiconductor pattern, the doped region having a differentconductivity type from the semiconductor pattern, and a connectionregion directly connected to the semiconductor pattern, the connectionregion having the same conductivity type as the semiconductor pattern.

The lower structure may include a substrate and a selection transistorinterposed between the substrate and the upper structure, the selectiontransistor including a selection semiconductor pattern directlyconnected to the semiconductor pattern, and the bottom surface of theinsulating spacer being positioned at a vertical level equivalent to orhigher than an uppermost surface of the selection semiconductor pattern.

The lower structure may include three-dimensionally arranged lowermemory devices and a pad pattern interposed between the lower memorydevices and the semiconductor pattern, the bottom surface of theinsulating spacer being positioned at a vertical level equivalent to orhigher than an uppermost surface of the pad pattern.

The upper structure may further include interlayer dielectric patternssequentially stacked on the lower structure and interposed between theconductive patterns, and an intermediate layer interposed between theconductive pattern and the semiconductor pattern, the insulating spacerbeing interposed between the interlayer dielectric pattern and thesemiconductor pattern.

A lowermost layer of the interlayer dielectric patterns may beinterposed between a lowermost layer of the conductive patterns and thelower structure, the lowermost layer of the interlayer dielectricpatterns being in direct contact with the semiconductor pattern.

The lowermost layer of the interlayer dielectric patterns may include atleast one of a silicon oxide layer or a high-k dielectric layer.

The lowermost layer of the interlayer dielectric patterns may includealuminum oxide.

A distance between the conductive pattern and the lower structure may besmaller than a thickness of the interlayer dielectric pattern.

The layer may extend horizontally from a region between the conductivepattern and the semiconductor pattern to cover top and bottom surfacesof the conductive pattern.

The intermediate layer may include a tunnel insulating layer, a blockinginsulating layer, and a charge storing layer interposed between thetunnel insulating layer and the blocking insulating layer, and each ofthe tunnel insulating layer and the blocking insulating layer mayinclude an insulating layer having a band gap greater than the chargestoring layer, the blocking insulating layer having an effectivedielectric constant greater than the tunnel insulating layer.

The insulating spacer may include a plurality of portions, each portionbeing locally interposed between the semiconductor pattern and theinterlayer dielectric patterns, the portions of the insulating spacerbeing vertically separated by the intermediate layer.

The insulating spacer and the intermediate layer may define a memorylayer including a tunnel insulating layer, a blocking insulating layer,and a charge storing layer interposed between the tunnel insulatinglayer and the blocking insulating layer, and each of the tunnelinsulating layer and the blocking insulating layer includes aninsulating layer having a band gap greater than the charge storinglayer, the blocking insulating layer having an effective dielectricconstant greater than the tunnel insulating layer.

The insulating spacer may include the tunnel insulating layer, theintermediate layer includes the blocking insulating layer, and at leastone of the insulating spacer and the intermediate layer includes thecharge storing layer.

The semiconductor pattern may include a semiconductor core inserted intothe lower structure through the insulating spacer, a vertical length ofthe semiconductor core being longer than that of the insulating spacer.

The upper structure may further include a lowermost interlayerdielectric pattern interposed between a lowermost layer of theconductive patterns and the lower structure, the semiconductor corehaving a surface in direct contact with a sidewall of the lowermostinterlayer dielectric pattern.

The semiconductor pattern may further include a semiconductor spacerinterposed between the insulating spacer and the semiconductor core.

The semiconductor core may include an extended portion covering a lowersidewall of the semiconductor spacer and having a top surface located onthe uppermost top surface of the lower structure.

The device may further include an insulating gap-filling patterninserted into the semiconductor core, the insulating gap-filling patternhaving a vertical length greater than the upper structure.

The lower structure may have a hole completely filled with thesemiconductor core.

According to other example embodiments of the inventive concepts, athree-dimensional semiconductor device may include an upper structure ona lower structure, the upper structure including conductive patterns, asemiconductor pattern extending through an opening in the upperstructure, the semiconductor pattern being perpendicular to andconnected to the lower structure, and an insulating spacer between thesemiconductor pattern and a sidewall of the opening, a space in a bottomof the upper structure separating a lowermost edge of the insulatingspacer and an uppermost surface of the lower structure.

According to other example embodiments of the inventive concepts, amethod of fabricating a three-dimensional semiconductor device mayinclude forming an upper structure on a lower structure, the upperstructure including conductive patterns, forming a semiconductor patternconnected to the lower structure through the upper structure, andforming an insulating spacer between the semiconductor pattern and theupper structure, such that a bottom surface of the insulating spacer ispositioned at a vertical level equivalent to or higher than an uppermostsurface of the lower structure.

Forming the upper structure on the lower structure may include forming alayer stack on the lower structure, forming the insulating spacer mayinclude forming an insulating layer vertically inserted into the layerstack, and etching a lower region of the insulating layer to form theinsulating spacer, such that the insulating spacer exposes a lowersidewall of the layer stack, and forming the semiconductor patternincludes forming the semiconductor pattern in the insulating spacer,such that the semiconductor pattern is directly connected to the lowerstructure through the layer stack.

Forming the insulating layer may include forming an opening through thelayer stack to expose the lower structure, and forming the insulatinglayer on an inner wall of the opening.

Forming the layer stack may include forming a plurality of horizontallayers sequentially deposited on the lower structure, and forming theinsulating layer may include forming an opening in the layer stack, andforming the insulating layer on an inner wall of the opening, such thatthe opening is spaced apart from the lower structure, and such that atleast one of the horizontal layers remains between a bottom surface ofthe opening and the lower structure.

Forming the semiconductor pattern may further include etching thehorizontal layer remaining below the opening to expose the lowerstructure.

Forming one of the horizontal layers may include forming a layer ofaluminum oxide as an etch stop layer during formation of the opening.

Forming the layer stack may include forming alternating first horizontallayers and second horizontal layers on the lower structure, the firsthorizontal layers being formed of silicon oxide, and the secondhorizontal layers being formed of a material having an etch selectivitywith respect to the first horizontal layers.

Forming the layer stack may include forming one of the first horizontallayers as a lowermost layer.

Forming the layer stack may include forming one of the second horizontallayers as a lowermost layer.

The method may further include, after forming the semiconductor pattern,removing the second horizontal layers to form recess regions exposing asidewall of the insulating spacer between the first horizontal layers,and forming conductive patterns in the recess regions.

The method may further include, before forming the conductive patterns,forming an intermediate pattern in the recess region, such that theintermediate pattern and the insulating spacer define a memory layer.

The method may further include, before forming the conductive patterns,etching the exposed insulating spacer to expose a sidewall of thesemiconductor pattern, and forming an intermediate pattern to cover theexposed sidewall of the semiconductor pattern, such that the insulatingspacer remains in regions localized between the semiconductor patternand the first horizontal layers.

Forming the insulating spacer may include forming a layer of at leastone material having an etch selectivity with respect to the secondhorizontal layer.

Forming the semiconductor pattern may include forming a semiconductorspacer to penetrate the insulating spacer, and forming a semiconductorcore directly connected to the lower structure through the semiconductorspacer.

The semiconductor spacer may be used as an etch mask exposing the lowerregion of the insulating layer, during formation of the insulatingspacer.

Forming the insulating spacer may include exposing the lower structurethrough an insulating layer, and forming the semiconductor patternincludes forming a semiconductor core to cover an inner sidewall of theinsulating spacer and the exposed lower structure.

Forming the lower structure may include forming a semiconductorsubstrate, such that the semiconductor pattern is directly connected tothe semiconductor substrate.

Forming the semiconductor substrate may include forming a doped regionapart from the semiconductor pattern, the doped region having adifferent conductivity type from the semiconductor pattern, and forminga connection region directly connected to the semiconductor pattern, theconnection region having the same conductivity type as the semiconductorpattern.

Forming the lower structure may include forming a substrate and aselection transistor interposed between the substrate and the upperstructure, the selection transistor including a selection semiconductorpattern directly connected to the semiconductor pattern, and the bottomsurface of the insulating spacer being positioned at a vertical levelhigher than the uppermost top surface of the selection semiconductorpattern.

Forming the lower structure may include forming three-dimensionallyarranged lower memory devices and a pad pattern interposed between thelower memory devices and the semiconductor pattern, the bottom surfaceof the insulating spacer being positioned at a vertical level higherthan the uppermost top surface of the pad pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages will become more apparent tothose of ordinary skill in the art by describing in detail exemplaryembodiments with reference to the attached drawings, in which:

FIGS. 1 through 9 illustrate sectional views of stages in methods offabricating a three-dimensional semiconductor device according to afirst example embodiment;

FIG. 10 illustrates a sectional view of methods of fabricating athree-dimensional semiconductor device according to modifications of thefirst example embodiment;

FIGS. 11 through 14 illustrate sectional views of three-dimensionalsemiconductor devices fabricated by a method based on the modificationsof the first example embodiment;

FIGS. 15 through 17 illustrate sectional views of stages in methods offabricating a three-dimensional semiconductor device according to asecond example embodiment;

FIG. 18 illustrates a sectional view of a method of fabricating athree-dimensional semiconductor device according to modifications of thesecond example embodiment;

FIGS. 19 through 24 illustrate sectional views of stages in methods offabricating a three-dimensional semiconductor device according to athird example embodiment;

FIGS. 25 through 28 illustrate sectional views of stages in methods offabricating a three-dimensional semiconductor device according to firstand second modifications of the third example embodiment;

FIGS. 29 through 31 illustrate sectional views of stages in methods offabricating a three-dimensional semiconductor device according to afourth example embodiment;

FIGS. 32 through 36 illustrate sectional views of stages in methods offabricating a three-dimensional semiconductor device according to firstto fourth modifications of the fourth example embodiment;

FIGS. 37 and 38 illustrate sectional views of stages in methods offabricating a three-dimensional semiconductor device according to afifth example embodiment;

FIG. 39 illustrates a sectional view provided to exemplarily describeother modifications of the previously-described embodiments;

FIGS. 40 through 46 illustrate sectional views of stages in methods offabricating a three-dimensional semiconductor device according to asixth example embodiment;

FIG. 47 illustrates a sectional view of a method of fabricating athree-dimensional semiconductor device according to modifications of thesixth example embodiment;

FIG. 48 illustrates a schematic sectional view of three-dimensionalsemiconductor devices according to a seventh example embodiment;

FIGS. 49 through 51 illustrate schematic sectional views ofthree-dimensional semiconductor devices according to modifications ofthe seventh example embodiments;

FIG. 52 illustrates a schematic diagram of a current pathway through asemiconductor device according to example embodiments;

FIG. 53 illustrates a schematic diagram of a current pathway through acomparative semiconductor device;

FIG. 54 illustrates a block diagram of memory cards equipped withsemiconductor memory devices according to example embodiments; and

FIG. 55 illustrates a block diagram of information processing systemsincluding memory systems according to example embodiments of theinventive concepts.

It should be noted that these figures are intended to illustrate thegeneral characteristics of methods, structure and/or materials utilizedin certain example embodiments and to supplement the written descriptionprovided below. These drawings are not, however, to scale and may notprecisely reflect the precise structural or performance characteristicsof any given embodiment, and should not be interpreted as defining orlimiting the range of values or properties encompassed by exampleembodiments. For example, the relative thicknesses and positioning ofmolecules, layers, regions and/or structural elements may be reduced orexaggerated for clarity. The use of similar or identical referencenumbers in the various drawings is intended to indicate the presence ofa similar or identical element or feature.

DETAILED DESCRIPTION

Example embodiments will now be described more fully hereinafter withreference to the accompanying drawings; however, they may be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art.

In the drawing figures, the dimensions of layers and regions may beexaggerated for clarity of illustration. It will also be understood thatwhen a layer or element is referred to as being “on” another layer orsubstrate, it can be directly on the other layer or substrate, orintervening layers may also be present. In addition, it will also beunderstood that when a layer is referred to as being “between” twolayers, it can be the only layer between the two layers, or one or moreintervening layers may also be present. Further, it will be understoodthat when a layer is referred to as being “connected” or “coupled” toanother element, it can be directly connected or coupled to the otherelement or intervening elements may be present. Other words used todescribe the relationship between elements or layers should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” “on” versus “directlyon”). Like reference numerals refer to like elements throughout.

As used herein the term “and/or” includes any and all combinations ofone or more of the associated listed items. It will also be understoodthat, although the terms “first”, “second”, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms are only used to distinguish oneelement, component, region, layer or section from another element,component, region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of example embodiments.

Spatially relative teems, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises”, “comprising”, “includes” and/or “including,” if usedherein, specify the presence of stated features, integers, steps,operations, elements and/or components, but do not preclude the presenceor addition of one or more other features, integers, steps, operations,elements, components and/or groups thereof.

Example embodiments of the inventive concepts are described herein withreference to cross-sectional illustrations that are schematicillustrations of idealized embodiments (and intermediate structures) ofexample embodiments. As such, variations from the shapes of theillustrations as a result, for example, of manufacturing techniquesand/or tolerances, are to be expected. Thus, example embodiments of theinventive concepts should not be construed as limited to the particularshapes of regions illustrated herein but are to include deviations inshapes that result, for example, from manufacturing. For example, animplanted region illustrated as a rectangle may have rounded or curvedfeatures and/or a gradient of implant concentration at its edges ratherthan a binary change from implanted to non-implanted region. Likewise, aburied region formed by implantation may result in some implantation inthe region between the buried region and the surface through which theimplantation takes place. Thus, the regions illustrated in the figuresare schematic in nature and their shapes are not intended to illustratethe actual shape of a region of a device and are not intended to limitthe scope of example embodiments.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which example embodiments of theinventive concepts belong. It will be further understood that terms,such as those defined in commonly-used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and will not be interpreted in anidealized or overly formal sense unless expressly so defined herein.

First Example Embodiments

FIGS. 1 through 9 are sectional views of stages in a method offabricating a three-dimensional semiconductor device according to afirst example embodiment.

Referring to FIG. 1, a layer stack 100 may be formed on a lowerstructure 10. In some embodiments, the lower structure 10 may be asubstrate formed of, e.g., a semiconductor material, an insulatingmaterial, or a semiconductor or conductive material covered with aninsulating layer. For example, the lower structure 10 may be a siliconwafer.

In other embodiments, the lower structure 10 may further include atleast one transistor interposed between the substrate and the layerstack 100. In the following description, for easier understanding ofexample embodiments of the inventive concepts, example embodiments maybe described with the layer stack 100 directly formed on the lowerstructure 10 or the substrate. However, example embodiments of theinventive concepts are not limited thereto.

The layer stack 100 may include a plurality of interlayer dielectrics120 and a plurality of sacrificial layers 130. The interlayerdielectrics 120 and the sacrificial layers 130 may be stacked in analternating manner, as shown in FIG. 1. According to the presentembodiments, one of the interlayer dielectrics 120 may be used as thelowermost layer of the layer stack 100. That is, one of the interlayerdielectrics 120 may be in direct contact with the lower structure 10,and the sacrificial layer 130 may be spaced apart from the lowerstructure 10.

The sacrificial layer 130 may include at least one material with an etchselectivity with respect to the interlayer dielectric 120. In otherwords, the interlayer dielectric 120 may include a material that isetched at a slower rate than the sacrificial layer 130 with respect toan etchant for etching the sacrificial layer 130. The etch selectivitymay be quantitatively expressed as a ratio of an etch speed of amaterial of the sacrificial layer 130 to a material of the interlayerdielectric 120. In some embodiments, the sacrificial layer 130 may beone or more materials providing an etch selectivity of about 1:10 toabout 1:200, e.g., about 1:30 to about 1:100, with respect to one ormore materials of the interlayer dielectric 120. For example, theinterlayer dielectric 120 may be at least one of a silicon oxide and asilicon nitride, and the sacrificial layer 130 may be at least one ofsilicon, a silicon oxide, a silicon carbide, and silicon nitride. Thesacrificial layer 130 may be selected to be a different material fromthe interlayer dielectric 120. In the following description, for easierunderstanding of example embodiments of the inventive concepts, exampleembodiments will be described with respect to an interlayer dielectric120 including silicon oxide and to a sacrificial layer 130 includingsilicon nitride. However, example embodiments are not limited to siliconoxide and silicon nitride, and each layer is not limited to a singlematerial.

Referring to FIG. 2, openings 105 may be formed to penetrate the layerstack 100. In some embodiments, the openings 105 may be formed to have,e.g., a hole shape. Each of the openings 105 may be formed to have ashape having a depth that is at least five times its width, e.g., anaspect ratio of about 5. According to the present embodiments, theopenings 105 may be two-dimensionally formed on the top surface (i.e.,the xy plane) of the lower structure 10. For example, each opening 105may be an isolated region spaced apart from other openings 105 alongeach of the x and y directions.

In other embodiments, each of the openings 105 may include, e.g., ahexahedral portion, in which its section projected on the top surface(i.e., the xy plane) of the lower structure 10 may have an aspect ratiogreater than about 5. For instance, the opening 105 may be formed tohorizontally cross or cut the layer stack 100.

The forming of the openings 105 may include forming a mask patterndefining positions of the openings 105 on the layer stack 100 and, e.g.,anisotropically etching the layer stack 100 using the mask pattern as anetch mask.

Since the layer stack 100 may include two kinds of different layers, thesidewall of the opening 105 may not be completely perpendicular withrespect to the top surface of the lower structure 10, unlike that shownin FIG. 2. For example, the opening 105 may be tapered downwardly, i.e.,the width of the opening 105 may decrease with decreasing distance fromthe lower structure 10. This non-uniform width of the opening 105 maycause non-uniformity in operational characteristics ofthree-dimensionally arranged transistors. Detailed description of thisnon-uniformity and methods of improving the same may be disclosed inU.S. patent application Ser. No. 12/420,518, the entire contents ofwhich are incorporated as part of this application.

According to the present embodiments, the opening 105 may be formed toexpose the top surface of the lower structure 10. In addition, the lowerstructure 10 below the opening 105 may be recessed due to over-etchduring the anisotropic etching of the layer stack 100 to have a recessedhole RH. For example, the opening 105 and the recessed hole RH mayoverlap and have same widths to define a uniform tunnel structure.

Referring to FIG. 3, a vertical layer 150 and a first semiconductorlayer 160 may be sequentially formed to cover inner walls of theopenings 105 and the recessed hole RH. The vertical layer 150 and thefirst semiconductor layer 160 may be conformally formed on the layerstack 100, i.e., may coat the inner walls of the openings 105 withoutcompletely filling the opening 105. As used herein, conformality is alayer property describing how well the topography of the underlyingsurface is replicated. For example, a conformal layer has asubstantially same shape as its underlying surface, i.e., the surface itcovers, and/or has a substantially same thickness throughout. Forexample, the vertical layer 150 and the first semiconductor layer 160may be formed to have a thickness of about, e.g., 1/50 to ⅕ of the widthof the opening 105.

According to some aspects of the inventive concepts, the vertical layer150 may be formed to have a single- or multi-layered structure. Forexample, the vertical layer 150, i.e., an insulating spacer 150, mayinclude at least one of layers constituting a memory element of a chargetrap type nonvolatile memory transistor. According to other aspects ofthe inventive concepts, the vertical layer 150 may be formed of aninsulating material having an etch selectivity with respect to thesacrificial layer 130. Example embodiments of the inventive concepts maybe diversely classified according to the layers of the vertical layer150, as will be described in more detail below with reference to Table 1and FIGS. 11 through 14.

The first semiconductor layer 160 may be a semiconductor layer (e.g., apolycrystalline silicon layer) formed using one of, for example, atomiclayer deposition (ALD) and chemical vapor deposition (CVD). In someembodiments, the first semiconductor layer 160 may be, for example, oneof an organic semiconductor layer and carbon nano structures.

Referring to FIG. 4, the first semiconductor layer 160 and the verticallayer 150 may be patterned to form a first semiconductor pattern 165 (ora semiconductor spacer) and a vertical pattern 155 (or an insulatingspacer) exposing the inner wall of the recessed hole RH again.

Formation of the vertical pattern 155 and the first semiconductorpattern 165 may include anisotropically etching the first semiconductorlayer 160 and the vertical layer 150 to expose the top surface of thelower structure 10 at the bottom of the openings 105. The verticalpattern 155 and the first semiconductor pattern 165 may be formed tohave, e.g., a cylindrical shape with open ends. Although not depicted,the top surface of the lower structure 10 exposed by the semiconductorpattern 165 may be additionally recessed by over etching during theanisotropic etching of the first semiconductor layer 160.

In some embodiments, an exposed surface of the vertical pattern 155 maybe further etched using the first semiconductor pattern 165 as an etchmask. In this case, as shown in FIG. 4, an undercut region may be formedbelow the first semiconductor pattern 165, and the vertical pattern 155may have a vertical length shorter than the first semiconductor pattern165. In other words, a distance between a bottom edge 155 a of thevertical pattern 155 to a bottom of the opening 105 may be larger than adistance between an uppermost surface 10 a of the lower structure 10 tothe bottom of the opening 105, so the edge 155 a may be spaced apartfrom the upper most surface 10 a. That is, the vertical pattern 155 mayextend only along an upper part of the lowermost dielectric layer 120,so a bottom part of the lowermost dielectric layer 120 may be betweenthe edge 155 a and the uppermost surface 10 a of the lower structure 10.

According to the present embodiments, as shown in FIG. 4, the undercutregion may be formed to expose at least a lower sidewall of the layerstack 100. In other words, a bottom surface of the vertical pattern 155may be positioned at a level higher than a bottom surface of the layerstack 100, so the lower sidewall of the layer stack 100, i.e., a lowerportion of the lowermost dielectric layer 120, may be exposed.

In addition, a top surface of the layer stack 100 may be exposed byanisotropically etching the first semiconductor layer 160 and thevertical layer 150. As a result, each of the vertical patterns 155 andeach of the first semiconductor patterns 165 may be localized within thecorresponding one of the openings 105. For instance, the verticalpatterns 155 and the first semiconductor pattern 165 may betwo-dimensionally arranged on the top surface of the lower structure 10.

Referring to FIG. 5, a second semiconductor layer 170 and a gap-fillingpattern 185 may be sequentially formed on the resultant structureprovided with the vertical pattern 155.

The second semiconductor layer 170 may be a semiconductor layer (e.g., apolycrystalline silicon layer) formed using one of, for example, ALD andCVD. In some embodiments, the second semiconductor layer 170 may beconformally formed not to fill completely the opening 105. Since thelower sidewall of the layer stack 100 is partially exposed by theundercut region as described above, the second semiconductor layer 170may be formed in direct contact with the exposed sidewall of the layerstack 100.

The gap-filling pattern 185 may be formed to fill, e.g., completelyfill, the opening 105 provided with the second semiconductor layer 170and may be an insulating layer formed using spin-on-glass (SOG)technique or a silicon oxide layer. In some embodiments, a hydrogenannealing step for thermally treating the structure including the secondsemiconductor layer 170 under a gas atmosphere including hydrogen and/orheavy hydrogen may be performed (e.g., before the formation of thegap-filling pattern 185). Crystal defects in the first semiconductorpattern 165 and the second semiconductor layer 170 may be cured and/orreduced during the hydrogen annealing.

Referring to FIG. 6, trenches 200 may be formed to penetrate the layerstack 100 and expose sidewalls of the sacrificial layers 130 and theinterlayer dielectrics 120. The trenches 200 may be spaced apart fromthe openings 105 and cross between the openings 105.

The formation of the trenches 200 may include forming an etch mask 190on the layer stack 100, and anisotropically etching the layer stack 100to expose the top surface of the lower structure 10. As shown, the lowerstructure 10 under the trench 200 may be recessed by over-etching duringthe anisotropic etching of the layer stack 100.

In some embodiments, a pair of the trenches 200 may be formed at bothsides of each of the openings 105. For instance, the openings 105disposed between the pair of the trenches 200 may be spaced thesubstantially same distance apart from one of the trenches 200. Butexample embodiments of the inventive concepts may not be limitedthereto. For example, in the openings 105 disposed between the pair ofthe trenches 200, some may be different from others in terms of adistance from one of the trenches 200.

In some embodiments, a second semiconductor pattern 175 and a pad PD maybe formed before the formation of the etch mask 190. The secondsemiconductor pattern 175 may be formed by patterning the secondsemiconductor layer 170 and may be localized within the opening 105. Thepad PD may be formed to be connected to the first and secondsemiconductor patterns 165 and 175. In some embodiments, the formationof the pad PD may include recessing upper portions of the first andsecond semiconductor patterns 165 and 175 and filling the recessedregion with the pad PD. The pad PD may be formed of a semiconductormaterial having a different conductivity type from the first and secondsemiconductor patterns 165 and 175. Since the second semiconductorpattern 175 may be formed by patterning the second semiconductor layer170 as described above, the second semiconductor pattern 175 may beformed in direct contact with the lower sidewall of the layer stack 100exposed by the undercut region, i.e., as the second semiconductor layer170.

Referring to FIG. 7, recess regions 210 may be formed between theinterlayer dielectrics 120 by selectively removing the sacrificiallayers 130 exposed by the trench 200. The recess regions 210 may be gapregions extending laterally from the trenches 200, and may be formed toexpose the sidewalls of the vertical patterns 155. An outer boundary ofthe recess region 210 may be defined by the interlayer dielectrics 120and the trenches 200, and an internal boundary thereof may be defined bythe vertical patterns 155 vertically penetrating the recess regions 210.

Formation of the recess regions 210 may include horizontally etching thesacrificial layers 130 using, for example, an etchant and/or etchprocess with etch selectivity to the interlayer dielectrics 120 and thevertical patterns 155. For example, if the sacrificial layers 130 aresilicon nitride layers and the interlayer dielectrics 120 are siliconoxide layers, the horizontal etch may be performed using an etchantincluding phosphoric acid.

Referring to FIG. 8, an intermediate layer 220 may be formed to cover aninner wall of the recess region 210, e.g., the intermediate layer 220may conformally coat the resultant structure on the lower structure 10to trace each recess region 210. Then, conductive patterns 230 may beformed to fill the remaining space of the recess region 210, i.e., onthe intermediate layer 220. The formation of the intermediate layer 220and the conductive patterns 230 may include sequentially forming theintermediate layer 220 and a conductive layer to cover, e.g., and fill,the recess regions 210, and then removing the conductive layer from thetrenches 200, so the conductive patterns 230 remain in the recessregions 210.

According to the present embodiments, before the formation of theintermediate layer 220, the vertical pattern 155 exposed by the recessregion 210 may be further etched to expose a sidewall of the firstsemiconductor pattern 165. In this case, the intermediate layer 220 maybe in direct contact with the exposed sidewall of the firstsemiconductor pattern 165, as shown, and the vertical pattern 155 mayinclude a plurality of portions vertically separated by the intermediatelayer 220.

The intermediate layer 220 may be formed to have a single- ormulti-layered structure, similar to the vertical layer 150. In someembodiments, the intermediate layer 220 may include a blockinginsulating layer of the charge trap type nonvolatile memory transistor.In other embodiments, the intermediate layer 220 may further include acharge storing layer and/or a tunnel insulating layer of the charge traptype nonvolatile memory transistor.

The conductive layer (on the intermediate layer 220) may be formed of,for example, at least one of doped silicon, metallic materials, metalnitrides, and/or metal silicide. For example, the conductive layer maybe formed of a tantalum nitride layer and/or a tungsten layer.

In some embodiments, the conductive layer may be formed to conformallycover the inner walls of the trench 200, and formation of the conductivepattern 230 may include removing the conductive layer in the trench 200using, for example, an isotropic etch. In other embodiments, theconductive layer may be formed to fill the trench 200, and formation ofthe conductive pattern 230 may include, for example, an anisotropicetching of the conductive layer in the trench 200.

According to example embodiments of the inventive concepts with respectto a FLASH memory, doped regions 240 may be formed after the formationof the conductive patterns 230. The doped regions 240 may be formedthrough an ion implantation process, and may be formed in the lowerstructure 10 exposed through the trench 200.

The doped regions 240 may be formed to have a different conductivitytype from the first and second semiconductor patterns 165 and 175. As aresult, the doped region 240 may form a pn junction in conjunction withthe lower structure 10 and/or the second semiconductor layer 170. Inother embodiments, a region of the lower structure 10 in contact, e.g.,direct contact, with the second semiconductor pattern 175 (hereinafter,a contact region) may have the same conductivity type as the secondsemiconductor pattern 175.

In some embodiments, the doped regions 240 may be connected to eachother and may be in an equipotential state. In other embodiments, thedoped regions 240 may be electrically separated from each other. Instill other embodiments, the doped regions 240 may be classified into aplurality of source groups, each of which include at least one dopedregion, and the source groups may be electrically separated from eachother to be at different electric potentials.

Referring to FIG. 9, electrode separation patterns 250 may be formed tofill the trenches 200, upper plugs 260 may be formed to be connected tothe pads PD, respectively, and then upper interconnection lines 270 maybe formed to connect the upper plugs 260. The electrode separationpattern 250 may be formed of at least one of silicon oxide, siliconnitride, or silicon oxynitride. The upper plugs 260 may be formed of atleast one of doped silicon or metallic materials.

Each of the upper interconnection lines 270 may be electricallyconnected to the first and second semiconductor patterns 165 and 175 viathe upper plug 260 and may be formed to cross the conductive patterns230 or the trenches 200. According to example embodiments of a NANDFLASH memory device, the upper interconnection lines 270 may be used asbit lines coupled to upper portions of a plurality of cell strings.

Modifications of the First Example Embodiments

FIG. 10 is a sectional view illustrating methods of fabricating athree-dimensional semiconductor device according to modifications of thefirst example embodiment. For concise description, overlappingdescription of elements previously described with reference to FIGS. 1through 9 may be omitted.

Referring to FIG. 10, according to the present embodiments, theintermediate layer 220 may be formed to cover the exposed sidewall ofthe vertical pattern 155, unlike the embodiments previously describedwith reference to FIG. 8. That is, the step of removing a portion of thevertical pattern 155 exposed by the recess region 210 may be omitted. Inthis case, as shown, the vertical pattern 155 may remain between theintermediate layer 220 and the first semiconductor pattern 165.

According to example embodiments for realizing a memory device, theintermediate layer 220 and the vertical pattern 155 may include astructure for storing information (hereinafter, a memory layer), asshown in FIGS. 11 through 14. For example, according to exampleembodiments of a charge trap type nonvolatile memory device, theintermediate layer 220 and the vertical pattern 155 may be part of amemory layer of a memory cell transistor. The number and materials oflayers in each of the intermediate layer 220 and the vertical pattern155 may vary, and based on this diversity, example embodiments of theinventive concepts may be classified into several example embodiments.For example, example embodiments of the inventive concepts related tothe memory layer may be classified as in the following Table 1.

TABLE 1 Memory layer Related Vertical Pattern Intermediate Layer FigureTIL CL CPL BIL FIG. 12 TIL CL BIL FIG. 11 TIL CL BIL FIG. 13 TIL CL CPLBIL1 BIL2 TIL CL BIL1 BIL2 FIG. 14 TIL CL BIL1 BIL2 TIL: tunnelinsulating layer CL: charge storing layer BIL: blocking insulating layerCPL: capping layer

As shown in Table 1, the memory layer may include a tunnel insulatinglayer TIL, a charge storing layer CL, and a blocking insulating layerBIL. Layers of the memory layer may be formed using a depositiontechnique providing, for example, excellent and/or improved stepcoverage property (e.g., a CVD and/or ALD technique).

In some embodiments, the charge storing layer CL may be used as part ofthe vertical pattern 155, but in other embodiments the charge storinglayer CL may be used as part of the intermediate layer 220. Furthermore,the memory layer may further include a capping layer CPL that isinterposed between the charge storing layer CL and the blockinginsulating layer BIL and is used as part of the vertical pattern 155.

In some embodiments, each of the tunnel insulating layer TIL, the chargestoring layer CL, and the blocking insulating layer BIL may be formed bya single deposition process, thereby having a single-layered structure.In other embodiments, at least one of them may be formed by a pluralityof separated layer-forming processes, thereby having a multi-layeredstructure. For example, as shown in Table 1, the blocking insulatinglayer BIL may include a first blocking insulating layer BIL1 and asecond blocking insulating layer BIL2.

The charge storing layer CL may be one or more insulating layers withabundant trap sites and/or one or more insulating layers with nanoparticles. For example, the charge storing layer CL may include one of atrap insulating layer or an insulating layer with a floating gateelectrode or conductive nano dots. In some embodiments, the chargestoring layer CL may include a silicon nitride layer, a siliconoxynitride layer, a silicon-rich nitride layer, a nano crystallinesilicon layer, and/or a laminated trap layer.

The tunnel insulating layer TIL may be one of materials with a higherband gap than the charge storing layer CL. For example, the tunnelinsulating layer TIL may be a silicon oxide layer. The tunnel insulatinglayer TIL may undergo a thermal treatment performed after a depositionprocess. The thermal treatment process may be, for example, a rapidthermal nitridation (RTN) process and/or an annealing process in anatmosphere including nitrogen and/or oxygen.

The blocking insulating layer BIL may include at least one of materialshaving a band gap smaller than the tunnel insulating layer TIL andhigher than the charge storing layer CL. For example, the blockinginsulating layer BIL may include one of high-k dielectrics, such asaluminum oxide and hafnium oxide. As a result, the blocking insulatinglayer BIL may have a dielectric constant higher than the tunnelinsulating layer TIL.

In the case that the blocking insulating layer BIL includes the firstand second blocking insulating layers BIL1 and BIL2, the first andsecond blocking insulating layers BIL1 and BIL2 may be differentmaterials. One of the first and second blocking insulating layers BIL1and BIL2 may be one of materials having a band gap smaller than thetunnel insulating layer TIL and higher than the charge storing layer CLand having a dielectric constant greater than the other. For example,one of the first and second blocking insulating layers BIL1 and BIL2 maybe formed of high-k dielectrics, such as aluminum oxide and hafniumoxide, and the other may be formed of silicon oxide. In this case, theblocking insulating layer BIL including the first and second blockinginsulating layers BIL1 and BIL2 may have an effective dielectricconstant greater than the tunnel insulating layer TIL.

The capping layer CPL may be formed of a material providing an etchselectivity with respect to the charge storing layer CL and/or thesacrificial layer 130. For example, if the sacrificial layer 130 is asilicon nitride layer, the capping layer CPL may be a silicon oxidelayer or an aluminum oxide layer. During a process for removing thesacrificial layer 130 to form the recess regions 210, the capping layerCPL may serve as an etch stop layer preventing and/or reducing etchdamage of the charge storing layer CL.

In the case that the capping layer CPL may remain between the conductivepattern 230 and the charge storing layer CL, the capping layer CPL maybe a material contributing to preventing leakage (e.g., back-tunneling)of electric charges stored in the charge storing layer CL. For example,the capping layer CPL may be one of a silicon oxide layer and a high-kdielectric layer.

Second Example Embodiments and Modifications Thereof

FIGS. 15 through 17 are sectional views illustrating methods offabricating a three-dimensional semiconductor device according to asecond example embodiment. FIG. 18 is a sectional view illustratingmethods of fabricating a three-dimensional semiconductor deviceaccording to modifications of the second example embodiment. For concisedescription, overlapping description of elements previously describedwith reference to FIGS. 1 through 14 may be omitted.

According to the present embodiments, as shown in FIG. 15, thesacrificial layer 130 may be the lowermost layer of the layer stack 100,i.e., the sacrificial layer 130 may be directly on the lower structure10. In this case, as shown in FIG. 16, the recess region 210 may beformed to expose the top surface of the lower structure 10 around thesecond semiconductor pattern 175. Therefore, the intermediate layer 220may be solely interposed between the conductive pattern 230 and thelower structure 10, as shown in FIGS. 17 and 18. That is, a portion ofthe intermediate layer 220 may be directly between a lowermostconductive pattern 230 and the lower structure 10.

In some embodiments, as described previously with reference to FIG. 8,before the formation of the intermediate layer 220, the vertical pattern155 exposed by the recess region 210 may be additionally etched toexpose the sidewall of the first semiconductor pattern 165. In thiscase, the intermediate layer 220 may be formed in direct contact withthe exposed sidewall of the first semiconductor pattern 165, as shown inFIG. 17, and the vertical pattern 155 may include a plurality ofportions vertically separated by the intermediate layer 220.

In other embodiments, as described previously with reference to FIG. 10,the additional etching of the vertical pattern 155 may be omitted. Thatis, the intermediate layer 220 may be formed to cover the sidewall ofthe vertical pattern 155. In this case, as shown in FIG. 18, thevertical pattern 155 may remain between the intermediate layer 220 andthe first semiconductor pattern 165 and may serve as the memory layeralong with the intermediate layer 220.

As described previously, the second semiconductor pattern 175 may beformed in direct contact with the lower sidewall of the layer stack 100exposed by the undercut region. Accordingly, the lowermost of the recessregions 210 may be formed to partially expose the sidewall of the secondsemiconductor pattern 175, as shown in FIG. 16. Therefore, theintermediate layer 220 may be in direct contact with the exposedsidewall of the second semiconductor pattern 175 in the lowermost recessregion 210, as shown in FIG. 17.

In modified embodiments, the sacrificial layer 130 and the lowerstructure 10 may be formed of materials, whose thermal expansioncoefficients are highly different from each other. In order to avoidtechnical problems related to the difference in the thermal expansioncoefficients, a buffer layer (not shown) may be interposed between thelayer stack 100 and the lower structure 10. In some embodiments, thebuffer layer may be thinner than the sacrificial layer 130. For example,if the sacrificial layer 130 is a silicon nitride layer and the lowerstructure 10 is a silicon wafer, the buffer layer may be a silicon oxidelayer, e.g., formed by oxidizing the silicon wafer.

In order to reduce complexity in the drawings, a portion of athree-dimensional semiconductor device spaced apart from the lowerstructure 10 (for instance, the upper interconnection lines 270) will beomitted in FIGS. 19 through 49. Those of ordinary skill in the art withknowledge of example embodiments will understand which elements may beomitted from both the accompanying drawings and descriptions offabricating methods. Additionally, for concise description, descriptionof overlapping elements previously described may be omitted. Sincethree-dimensional semiconductor devices described herein may befabricated through modifications of the above-mentioned fabricatingmethods and other different fabricating methods, all the describedelements of disclosed fabricating method may not necessarily beexplicitly included in description of three-dimensional semiconductordevices.

Third Example Embodiments and Modifications Thereof

FIGS. 19 through 24 are sectional views illustrating methods offabricating a three-dimensional semiconductor device according to athird example embodiment. FIG. 25 is a sectional view of methods offabricating a three-dimensional semiconductor device according to afirst modification of the third example embodiment. For concisedescription, overlapping description of elements previously describedwith reference to FIGS. 1 through 18 may be omitted.

According to the present embodiments, as shown in FIG. 19, the layerstack 100 may further include an underlying layer 90, and the opening105 may be formed to have a bottom surface positioned in the underlyinglayer 90. That is, a bottom of the opening 105 may be in the underlyinglayer 90, e.g., the opening 105 may not contact the lower structure 10.

The underlying layer 90 may be formed of an insulating material havingan etch selectivity with respect to at least one of the interlayerdielectric 120 or the sacrificial layer 130. For example, the underlyinglayer 90 may be an etch selectivity of silicon oxide, silicon nitride, ametal oxide, or a metal nitride. In some embodiments, the underlyinglayer 90 may include a high-k dielectric, e.g., aluminum oxide and/orhafnium oxide. In other embodiments, in the case that a layer of thelayer stack 100 formed directly on the underlying layer 90 is a siliconoxide layer, the underlying layer 90 may include at least one of siliconnitride or aluminum oxide. In still other embodiments, in the case thata layer of the layer stack 100 formed directly on the underlying layer90 is a silicon nitride layer, the underlying layer 90 may include atleast one of silicon oxide or aluminum oxide.

The formation of the opening 105 may include anisotropically etching theinterlayer dielectric 120 and the sacrificial layer 130 using an etchrecipe providing an etch selectivity with respect to the underlyinglayer 90. That is, the underlying layer 90 may serve as an etch stoplayer during the formation of the opening 105. As a result, the bottomsurface of the opening 105 may be formed at a level vertically spacedapart from the lower structure 10. That is, a portion of the underlyinglayer 90 may remain between the opening 105 and the lower structure 10.

Thereafter, the vertical layer 150 may be formed to cover the inner wallof the opening 105, as shown in FIG. 19, and then a through hole 106 maybe formed to penetrate a portion of the underlying layer 90 remainingbelow the opening 105, as shown in FIG. 20. During the formation of thethrough hole 106, the top surface of the lower structure 10 may berecessed below the opening 105. The formation of the through hole 106may include forming a first semiconductor layer to cover an inner wallof the vertical layer 150 and then anisotropically etching the firstsemiconductor layer, the vertical layer 150, and the remaining portionof the underlying layer 90 to expose the lower structure 10.

Accordingly, the vertical pattern 155 and the first semiconductorpattern 165 may be localized within a region, which is included in theopening 105 but not in the through hole 106. For instance, the verticalpattern 155 may be formed to have a spacer shape covering the inner wallof the opening 105, and a bottom surface thereof may be positioned at alevel equivalent to or higher than the top surface of the lowerstructure 10.

As shown in FIG. 21, the through hole 106 may be filled with the secondsemiconductor pattern 175 and the gap-filling pattern 185. Since thebottom surface of the vertical pattern 155 may be positioned at a levelequivalent to or higher than the top surface of the lower structure 10,as described above, the step of additionally etching the lower region ofthe vertical pattern 155, which was described with reference to FIG. 4,may be omitted. For all that, similar to the previously describedembodiments, the second semiconductor pattern 175 may be formed indirect contact with the lower sidewall of the layer stack 100. However,it is optional whether the additional etching step would be omitted ornot, and the additional etching step may be still performed in thepresent embodiments.

Thereafter, as shown in FIG. 22, the trenches 200 may be formed spacedapart from the first semiconductor patterns 165 to penetrate the layerstack 100, and then, as shown in FIG. 23, the sacrificial layers 130 maybe selectively removed to form the recess regions 210 exposing thesidewall of the vertical pattern 155. These steps may be performed byusing or modifying the method described with reference to FIGS. 6 and 7.In the meantime, since the interlayer dielectric 120 or the sacrificiallayer 130 is formed to have the etch selectivity with respect to theunderlying layer 90, a sidewall profile of the trench 200 may be changedfrom that shown in FIG. 22. For concise description, description on sucha variation related to the sidewall profile of the trench 200, which canbe easily expected by those of ordinary skill in the art, may beomitted.

According to the third embodiments of the inventive concepts, asdescribed with reference to FIG. 8, before the formation of theintermediate layer 220, the vertical pattern 155 exposed by the recessregion 210 may be further etched to expose the sidewall of the firstsemiconductor pattern 165. In this case, the intermediate layer 220 maybe in direct contact with the exposed sidewall of the firstsemiconductor pattern 165, as shown in FIG. 24, and the vertical pattern155 may include a plurality of portions vertically separated by theintermediate layer 220.

In other embodiments, as described previously with reference to FIG. 10,the additional etching of the vertical pattern 155 may be omitted. Thatis, the intermediate layer 220 may be formed to cover the sidewall ofthe vertical pattern 155. In this case, as shown in FIG. 25, thevertical pattern 155 may remain between the intermediate layer 220 andthe first semiconductor pattern 165 and may serve as the memory layeralong with the intermediate layer 220.

According to the present embodiments, as shown in FIG. 23, the recessregions 210 may be formed spaced apart from the second semiconductorpattern 175. And, as shown in FIGS. 24 and 25, the underlying layer 90may be interposed between the intermediate layer 220 and the lowerstructure 10, and the second semiconductor pattern 175 may be formed indirect contact with the lower sidewall of the underlying layer 90.

FIGS. 26 through 28 are sectional views illustrating methods offabricating a three-dimensional semiconductor device according to secondmodifications of the third example embodiment. For concise description,overlapping description of elements previously described with referenceto FIGS. 1 through 25 may be omitted.

According to the present embodiments, the through hole 106 may be formedwithout using the first semiconductor pattern 165, as shown in FIG. 26.For instance, the steps of forming the first semiconductor layer 160 andthe first semiconductor pattern 165 may be omitted, and the formation ofthe through hole 106 may include anisotropically etching the verticallayer 150 and the remaining portion of the underlying layer 90.Accordingly, the vertical pattern 155 may be localized within a region,which is included in the opening 105 but not in the through hole 106.Similar to the previously-described third embodiment, a bottom surfaceof the vertical pattern 155 may be positioned at a level equivalent toor higher than the top surface of the lower structure 10.

The through hole 106 may be filled with the second semiconductor pattern175 and the gap-filling pattern 185, as shown in FIG. 27. As the resultof the absence of the first semiconductor pattern 165, the outersidewall of the second semiconductor pattern 175 may be formed to be indirect contact with the entire inner sidewall of the vertical pattern155. In addition, below the vertical pattern 155, the secondsemiconductor pattern 175 may be formed to be in direct contact with thelower sidewall of the underlying layer 90.

Thereafter, the trenches 200 may be formed spaced apart from the secondsemiconductor pattern 175 to penetrate the layer stack 100, and then,the sacrificial layers 130 may be selectively removed to form the recessregions 210 exposing the sidewall of the vertical pattern 155. Thesesteps may be performed by using or modifying the method described withreference to FIGS. 22 and 23.

According to the present embodiments, as described with reference toFIG. 8, before the formation of the intermediate layer 220, the verticalpattern 155 exposed by the recess region 210 may be further etched toexpose the sidewall of the first semiconductor pattern 165. In thiscase, the intermediate layer 220 may be in direct contact with theexposed sidewall of the first semiconductor pattern 165, as shown inFIG. 28, and the vertical pattern 155 may include a plurality ofportions vertically separated by the intermediate layer 220.

Fourth Example Embodiments and Modifications Thereof

FIGS. 29 through 31 are sectional views illustrating methods offabricating a three-dimensional semiconductor device according to afourth example embodiment. FIG. 32 is a sectional view illustratingmethods of fabricating a three-dimensional semiconductor deviceaccording to first modifications of the fourth example embodiments. Forconcise description, overlapping description of elements previouslydescribed with reference to FIGS. 1 through 28 may be omitted.

According to the present embodiments, as shown in FIG. 29, theunderlying layer 90 may include a first underlying layer 91 and a secondunderlying layer 92 sequentially stacked on the lower structure 10. Thefirst underlying layer 91 may be different from the second underlyinglayer 92 in terms of material and/or thickness. For example, the firstunderlying layer 91 may be a silicon oxide layer, whose thickness issmaller than that of the second underlying layer 92.

In some embodiments, the second underlying layer 92 may be formed of aninsulating material having an etch selectivity with respect to at leastone of the interlayer dielectric 120 or the sacrificial layer 130. Forinstance, the second underlying layer 92 may be formed of thesubstantially same material as the underlying layer 90 in the thirdembodiments. Accordingly, the second underlying layer 92 may serve as anetch stop layer during the formation of the opening 105, and the bottomsurface of the opening 105 may be defined by the second underlying layer92.

In other embodiments, the second underlying layer 92 may be formed of amaterial, which can be etched along with the sacrificial layer 130during the formation of the recess regions. For instance, under an etchrecipe used to form the recess region, the second underlying layer 92may be formed of a material having an etch selectivity with respect tothe interlayer dielectric 120 but not having such an etch selectivitywith respect to the sacrificial layer 130. In this case, as shown inFIG. 30, the recess regions 210 may be formed to expose a top surface ofthe first underlying layer 91 and a portion of the lower sidewall of thesecond semiconductor pattern 175. The recess region 210 may be filledwith the intermediate layer 220 and the conductive patterns 230, asshown in FIGS. 31 and 32.

In some embodiments, as described with reference to FIG. 8, before theformation of the intermediate layer 220, the vertical pattern 155exposed by the recess region 210 may be further etched to expose thesidewall of the first semiconductor pattern 165. In this case, theintermediate layer 220 may be in direct contact with the exposedsidewall of the first semiconductor pattern 165, as shown in FIG. 31,and the vertical pattern 155 may include a plurality of portionsvertically separated by the intermediate layer 220.

In the case that the first underlying layer 91 does not have an etchselectivity with respect to the vertical pattern 155, the firstunderlying layer 91 may be removed during the etching of the verticalpattern 155. In this case, as shown in FIG. 31, the intermediate layer220 may be formed to directly cover the top surface of the lowerstructure 10.

In other embodiments, as described previously with reference to FIG. 10,the additional etching of the vertical pattern 155 may be omitted. Inthis case, as shown in FIG. 32, the vertical pattern 155 may remainbetween the intermediate layer 220 and the first semiconductor pattern165 and may serve as the memory layer along with the intermediate layer220. Furthermore, as shown in FIG. 32, a portion of the intermediatelayer 220 disposed between the lowermost conductive pattern and thesecond semiconductor pattern 175 may be in direct contact with both ofthe vertical pattern 155 and the second semiconductor pattern 175.

FIGS. 33 through 36 are sectional views illustrating methods offabricating a three-dimensional semiconductor device according to secondto fourth modifications of the fourth example embodiment. For concisedescription, overlapping description of elements previously describedwith reference to FIGS. 1 through 32 may be omitted.

According to second modifications of the fourth embodiments, theunderlying layer 90 may include the first underlying layer 91 and thesecond underlying layer 92, as described with reference to FIG. 29, butprocess steps after the formation of the underlying layer 90 may beperformed using the method described with reference to FIGS. 26 through28. For instance, the methods of fabricating a three-dimensionalsemiconductor device may be performed without formation of the firstsemiconductor pattern 165 described with reference to FIG. 30, and thus,the second semiconductor pattern 175 may be directly connected to thelower structure 10 through the vertical pattern 155, as shown in FIG.33. In addition, during formation of the recess region 210, the secondunderlying layer 92 and the sacrificial layer 130 may be removedtogether, such that the intermediate layer 220 may be formed in directcontact with the first underlying layer 91 and the second semiconductorpattern 175, as shown in FIG. 34.

According to third modifications of the fourth embodiments the firstunderlying layer 91 may be removed during the etching of the verticalpattern 155. As a result, as shown in FIG. 35, the intermediate layer220 may be formed to directly cover the top surface of the lowerstructure 10, without an interposition of the first underlying layer 91.

According to fourth modifications of the fourth embodiment, the step ofetching the vertical pattern 155 to expose the sidewall of the secondsemiconductor pattern 175 may be omitted. Accordingly, as shown in FIG.36, the vertical pattern 155 may remain between the intermediate layer220 and the second semiconductor pattern 175, and may serve as thememory layer along with the intermediate layer 220.

Fifth Example Embodiments and Modifications Thereof

FIGS. 37 and 38 are sectional views illustrating methods of fabricatinga three-dimensional semiconductor device according to fifth exampleembodiments of the inventive concepts. For concise description,overlapping description of elements previously described with referenceto FIGS. 1 through 36 may be omitted.

According to the present embodiments, as shown in FIG. 37, theunderlying layer 90 may include a first underlying layer 91 and a secondunderlying layer 92 sequentially stacked on the lower structure 10. Thefirst underlying layer 91 may be different from the second underlyinglayer 92 in terms of material and/or thickness. In view of this, theseembodiments may be identical to the previous embodiments described withreference to FIG. 29. However, unlike the previous embodiments, thefirst underlying layer 91 of the present embodiments may be thicker thanthe second underlying layer 92.

Similar to the previous embodiments, the second underlying layer 92 mayserve as an etch stop layer during the formation of the opening 105. Forexample, as shown in FIG. 37, the opening 105 may be formed to penetratethrough the second underlying layer 92, such that the bottom surfacethereof may be defined by the first underlying layer 91. In anotherexample, the opening 105 may be formed not to penetrate through thesecond underlying layer 92, such that the bottom surface of the openingmay be in the second underlying layer 92, as in the previousembodiments.

According to the present embodiments, the sacrificial layer 130 may be alayer of the layer stack 100 formed directly on the second underlyinglayer 92, unlike the previous embodiments described with reference toFIGS. 29 through 36. As a result, the first and second underlying layers91 and 92 may be interposed between the conductive pattern 230 and thelower structure 10, as shown in FIG. 38. These process steps may beperformed by using the method described with reference to FIGS. 19through 28.

According to other modifications of the present embodiments, althoughnot depicted, the intermediate layer 220 may be formed to verticallyseparate the vertical pattern 155 into a plurality of portions and to bein direct contact with the sidewall of the first semiconductor pattern165, similar to the structure shown in FIG. 24. According to still othermodifications of the present embodiments, the methods of fabricating athree-dimensional semiconductor device may be performed without formingthe first semiconductor pattern 165, and thus, the second semiconductorpattern 175 may be in direct contact with the inner sidewall of thevertical pattern 155, similar to the structure shown in FIG. 28 or FIG.34.

Other Modified Embodiments

FIG. 39 is a sectional view provided to exemplarily describemodifications of the previously-described first through fifthembodiments. That is, each of the first through fifth embodiments may bemodified to have the following technical features described withreference to FIG. 39.

The through hole 106 may be formed to have a downwardly tapered shape.For example, as shown in FIG. 39, a width of the through hole 106 in thelower structure 10 may decrease with an increase of depth, and thesecond semiconductor pattern 175 may be formed to completely fill thethrough hole 106 provided in the lower structure 10. Thus, the bottomsurface of the gap-filling pattern 185 may be formed at a levelequivalent to or higher than the top surface of the lower structure 10.

Sixth Example Embodiments and Modifications Thereof

FIGS. 40 through 46 are sectional views illustrating methods offabricating a three-dimensional semiconductor device according to asixth example embodiment. FIG. 47 is a sectional view illustratingmethods of fabricating a three-dimensional semiconductor deviceaccording to a modification of the sixth example embodiment. For concisedescription, overlapping description of elements previously describedwith reference to FIGS. 1 through 9 may be omitted.

According to the present embodiments, the lower structure 10 may includea substrate SUB and a lower layer stack disposed on the substrate SUB,as shown in FIG. 40. The lower layer stack may include lower horizontallayers 122 and lower sacrificial layers 132, which are alternatinglystacked on the substrate SUB. In addition, the lower structure 10 mayfurther include selection active patterns (SAP) connected to thesubstrate SUB through the lower horizontal layers 122 and the lowersacrificial layers 132.

In some embodiments, the lower horizontal layers 122 and the lowersacrificial layers 132 may be formed of substantially the same materialsas the interlayer dielectric 120 and the sacrificial layer 130,respectively, described with reference to FIG. 1. In other embodiments,the lower horizontal layer 122 may be formed of at least one conductivematerial. Technical features related to the selection active pattern SAPand the modified embodiments related to the lower horizontal layer 122may be realized using the methods disclosed in U.S. patent applicationSer. No. 13/072,078, filed on Mar. 25, 2011, the entire contents ofwhich are incorporated as part of this application.

Thereafter, as shown in FIG. 41, the layer stack 100 may be formed onthe resultant structure provided with the selection active pattern SAP.As shown in FIG. 42, the openings 105 may be formed through the layerstack 100 to expose the lower structure 10. In some embodiments, theopening 105 may be formed to expose a top surface of the selectionactive pattern SAP, as shown in FIG. 42. The top surface of theselection active pattern SAP may be recessed during the formation of theopening 105.

As shown in FIG. 43, the vertical pattern 155 and the firstsemiconductor pattern 165 may be formed in the opening 105. The verticalpattern 155 may be interposed between the first semiconductor pattern165 and the layer stack 100, and may be formed to expose the lowersidewall of the layer stack 100. The formation of the vertical pattern155 and the first semiconductor pattern 165 may be performed using themethods described with reference to FIGS. 3 and 4.

As shown in FIG. 44, the second semiconductor pattern 175 and thegap-filling pattern 185 may be formed in the opening 105 provided withthe vertical pattern 155 and the first semiconductor pattern 165. Thesecond semiconductor pattern 175 may be formed to cover the lowersidewall of the layer stack 100 exposed by the vertical pattern 155. Forinstance, the second semiconductor pattern 175 may include an extensionEXT interposed between the first semiconductor pattern 165 and the layerstack 100, e.g., the extension EXT may be continuous with the secondsemiconductor pattern 175 to surround a bottom edge of the firstsemiconductor pattern 165. For example, the extension EXT of the secondsemiconductor pattern 175 may extend in parallel to the firstsemiconductor pattern 165, and may be in contact, e.g., direct contact,with the layer stack 100, the first semiconductor pattern 165, and thevertical pattern 155. In some embodiments, the extension EXT may have atop surface located at a higher level than the bottom surface of thelayer stack 100 and the top surface of the selection active pattern SAP.The formation of the second semiconductor pattern 175 and thegap-filling pattern 185 may be performed using the methods describedwith reference to FIG. 5.

The trench 200 may be formed through the layer stack 100 to expose thelower structure 10. The formation of the trench 200 may be performedusing the methods described with reference to FIG. 6. In someembodiments, the trench 200 may be formed to penetrate the lowerhorizontal layers 122 and the lower sacrificial layers 132 and exposethe substrate SUB, as shown in FIG. 44.

The sacrificial layers 130 may be removed to form the recess regions 210exposing the sidewall of the vertical pattern 155, as shown in FIG. 45.The formation of the recess regions 210 may be performed using themethods described with reference to FIG. 7. As described above,according to some embodiments of the inventive concepts, the lowerhorizontal layer 122 and the lower sacrificial layer 132 may be formedof substantially the same materials as the interlayer dielectric 120 andthe sacrificial layer 130, respectively. In this case, as shown in FIG.45, the lower sacrificial layer 132 may be removed along with thesacrificial layers 130, such that lower recess regions 212 may be formedin the lower structure 10. In some embodiments, the lower recess regions212 may be formed to expose a sidewall of the selection active patternSAP.

As shown in FIGS. 46 and 47, the intermediate layer 220 and theconductive patterns 230 may be formed in the recess regions 210 and thelower recess regions 212. In some embodiments, the formation of theintermediate layer 220 and the conductive patterns 230 may be performedusing the methods described with reference to FIGS. 8 and 9. In thiscase, as shown in FIG. 46, the intermediate layer 220 may be formed todirectly cover the sidewall of the first semiconductor pattern 165 andthe sidewall of the selection active pattern SAP. In other embodiments,the formation of the intermediate layer 220 and the conductive patterns230 may be performed using the methods described with reference to FIG.10. In this case, as shown in FIG. 47, the intermediate layer 220 may beformed to directly cover the sidewall of the vertical pattern 155 andthe sidewall of the selection active pattern SAP. According to the sixthembodiment, the selection active pattern SAP may serve as a channelregion of a selection transistor (e.g., a ground selection transistor),and the conductive pattern 230 adjacent thereto may serve as a gateelectrode of the selection transistor.

It is noted that if the lower inner sidewall of the layer stack 100 isnot exposed, i.e., if the process of etching the lower portion of thevertical pattern 155 described with reference to FIG. 43 is omitted, thevertical pattern 155 may have a hook shape, i.e., a mirror-image of a“L” shape, having a portion remaining between the selection activepattern SAP and the second semiconductor pattern 175. In other words, alower portion of the vertical pattern 155 may contact the secondsemiconductor pattern 175 to cover, e.g., to completely overlap, abottom surface of the first semiconductor pattern 165. If the lowerportion of the vertical pattern 155 covers the bottom surface of thefirst semiconductor pattern 165, a path length of an electric currentpassing the first and second semiconductor patterns 165 and 175 and theselection active pattern SAP may increase, thereby increasing resistanceof the electric current path or reducing the operating current.

In addition, when the vertical pattern 155 is not etched and extendsinto the selection active pattern SAP, a portion of the selection activepattern SAP may surround lower regions of the first and secondsemiconductor patterns 165 and 175. That is, the portion of theselection active pattern SAP may be interposed between the conductivepattern 230 and the lower regions of the first and second semiconductorpatterns 165 and 175, thereby serving as a shielding element. In thiscase, the semiconductor device may exhibit increased resistance of theelectric current path or reduced operating current.

Seventh Example Embodiments and Modifications Thereof

FIG. 48 is a schematic sectional view illustrating three-dimensionalsemiconductor devices according to a seventh example embodiment. FIGS.49 through 51 are schematic sectional views of three-dimensionalsemiconductor devices according to modifications of the seventh exampleembodiment.

Referring to FIG. 48, a three-dimensional semiconductor device 500 mayinclude the lower structure 10 and an upper structure 20, which may beconfigured to have the substantially same structure as the lowerstructure 10, and may be sequentially stacked. In some embodiments, eachof the lower and upper structures 10 and 20 may be configured to includeelements disposed between the lower structure 10 and the upper plug 260in the previous embodiments described with reference to FIGS. 1 through47. For example, each of the lower and upper structures 10 and 20 mayinclude a plurality of the conductive patterns 230 located at differentlevels, as shown FIG. 48.

In addition, the three-dimensional semiconductor device 500 may includesemiconductor patterns SP vertically penetrating the lower and upperstructures 10 and 20, and vertical patterns 155 interposed between thelower and upper structures 10 and 20 and the semiconductor patterns SP.In some embodiments, the vertical pattern 155 in the upper structure 20may be formed to have a bottom surface positioned at a vertical levelequivalent to or higher than a top surface of the lower structure 10.

In some embodiments, the lower structure 10 may further include aconnection structure CNS for establishing an electric connection to theupper structure 20. The fabricating methods of the previous embodimentsdescribed with reference to FIGS. 1 through 47 may be used to form theconnection structure CNS, the semiconductor patterns SP, the verticalpatterns 155, and the lower and upper structures 10 and 20. For example,as exemplarily shown in FIG. 48, the lower and upper structures 10 and20 may be formed to have the three-dimensional semiconductor deviceaccording to the first embodiments described with reference to FIGS. 1through 8.

With regard to the method for forming the semiconductor patterns SP,e.g., first and second semiconductor patterns 165 and 175, the lower andupper structures 10 and 20 may be respectively formed by two methods ofthe previously described embodiments, which are selected to be differentfrom each other. For example, as shown in FIG. 50, the lower structure10 may be formed to have the structure of the embodiments described withreference to FIG. 32, and the upper structure 20 may be formed to havethe structure of the embodiments described with reference to FIG. 47.

In other embodiments, as shown in FIGS. 50 and 51, the intermediatelayer 220 may be formed to cover a top surface, a bottom surface, and aninner sidewall of the conductive pattern 230, but may be removed from anouter sidewall of the conductive pattern 230 to expose a sidewall of theinterlayer dielectric 120 adjacent to the trenches 200.

In still other embodiments, the second semiconductor pattern 175 may beformed to have a void VD, which may be filled with a gaseous medium,such as air. For example, as shown in FIG. 52, the void VD may be formedin a portion of the second semiconductor pattern 175 vertically disposedbelow the vertical pattern 155 and horizontally interposed between thefirst semiconductor pattern 165 and an inner wall of the opening 105.

FIGS. 52 and 53 are schematic diagrams presented to describe someaspects of the inventive concepts. According to example embodiments ofthe inventive concepts, the first and second semiconductor patterns 165and 175 may form a pathway 51 electrically connecting the lowerstructure 10 and the upper structure 20, in response to an electricsignal applied to the conductive patterns 230.

In some embodiments, the pathway 51 may be bent depending on aconnection structure between the lower structure 10 and the upperstructure 20, like the embodiments described with reference to FIGS. 9through 14. Therefore, as shown in FIG. 52, the pathway 51 may beconfigured to extend along a region adjacent to the conductive pattern230. As a result, an electric current passing through the pathway 51 canbe easily controlled by the conductive pattern 230.

In addition, according to example embodiments of the inventive concepts,since a bottom surface of the vertical pattern 155 is positioned at alevel equivalent to or higher than the top surface of the lowerstructure 10, it may be possible to prevent the electric pathway 51 frombeing elongated by the presence of the vertical pattern 155. Forinstance, as shown in FIG. 52, a path length between two points a and bdisposed on the pathway 51 may be equivalent to or smaller than 2 L,which is given by the absence of such a bending.

In contrast, if a vertical pattern (or an insulation spacer) extendsinto the lower structure 10, as illustrated in FIG. 53, a resultantelectric pathway 52 extends to surround the vertical pattern, therebyforming an elongated current pathway. In other words, the distancebetween the two points a and b in FIG. 53 may be increased, e.g., ascompared to the distance between the two points a and b in FIG. 52. Theincreased distance causes an increased electric pathway, which in turn,increases the electric resistance. In addition, since a portion of theelectric pathway 52 is formed along a region spaced apart from theconductive pattern 230, it may be hard to control an electric currentpassing through the electric pathway 52.

FIG. 54 is a block diagram illustrating memory cards 1200 includingflash memory devices 1210 according to example embodiments of theinventive concepts.

Referring to FIG. 54, the memory card 1200 for supporting a data storagecapability of high capacity may include a flash memory device 1210, forexample, including a 3D memory device as described with respect toexample embodiments illustrated in FIGS. 1-53. The memory card 1200according to example embodiments of the inventive concepts may include amemory controller 1220 controlling general data exchanges between a hostand the flash memory device 1210.

A RAM 1221, e.g., a SRAM, may be used as an operating memory of aprocessing unit 1222. A host interface 1223 may include a data exchangeprotocol of a host connected to a memory card 1200. An error correctionblock 1224 may detect and correct errors included in data read from amulti-bit flash memory device 1210. A memory interface 1225 mayinterface with the flash memory device 1210 of example embodiments ofthe inventive concepts. A processing unit 1222 may perform generalcontrol operations for data exchange of the memory controller 1220.Although not shown in the drawing, it is apparent to those skilled inthe art that the memory card 1200 may further include ROM (not shown)storing code data to interface with a host.

FIG. 55 is a block diagram illustrating information processing systems1300 including flash memory systems 1310 according to exampleembodiments of the inventive concepts.

Referring to FIG. 55, the flash memory system 1310 may be mounted on aninformation processing system, for example, a mobile device and/or adesktop computer. The information processing system 1300 may include aflash memory system 1310, a modem 1320, a central processing unit (CPU)1330, a RAM 1340, and a user interface 1350, electrically connected to asystem bus 1360. The flash memory system 1310 may be configuredsubstantially identical to the memory system and/or flash memory systemdescribed with respect to FIG. 54. Data processed by the CPU 1330 and/orinput from the outside may be stored in the flash memory system 1310. Amemory system 1310 may be a solid state drive SSD. The informationprocessing system 1300 may stably store a large amount of data in theflash memory system 1310. As reliability of the information processingsystem 1300 may be increased, the flash memory system 1310 may conserveresources used for error correction, and a data exchange function ofhigh speed may be provided to the information processing system 1310.Although not shown in the drawing, it is apparent to those of ordinaryskill in the art that the information processing system 1300 of exampleembodiments of the inventive concepts may include an applicationchipset, a camera image processor (CIS), and/or an input/output device.

A flash memory device and/or a memory system of example embodiments ofthe inventive concepts may be mounted using various kinds of packages.For instance, the flash memory device and/or the memory system may bemounted with packages such as Package on Package (PoP), Ball Grid Arrays(BGA), Chip Scale Packages (CSP), Plastic Leaded Chip Carrier (PLCC),Plastic Dual In-line Package (PDIP), Die in Waffle Pack, Die in WaferForm, Chip On Board (COB), Ceramic Dual In-line Package (CERDIP),Plastic Metric Quad Flat Pack (MQFP), Thin Quad Flat Pack (TQFP), SmallOutline Integrated Circuit (SOIC), Shrink Small Outline Package (SSOP),Thin Small Outline Package (TSOP), System In Package (SIP), Multi ChipPackage (MCP), Wafer-level Fabricated Package (WFP), and/or Wafer-levelProcessed Stack Package (WSP).

According to example embodiments of the inventive concepts, a verticalpattern may be interposed between an interlayer dielectric and asemiconductor pattern in terms of a horizontal position, and may have abottom surface positioned at a level equivalent to or higher than a topsurface of a lower structure in tennis of a vertical position.Accordingly, the entire inner wall of a hole, which is formed on the topsurface of the lower structure, may be in direct contact with asemiconductor pattern inserted therein. As a result, a length of anelectric pathway between the lower structure (e.g., a semiconductorsubstrate) and the semiconductor pattern may be decreased. That is, thestructure of the vertical pattern according to example embodiments mayfacilitate construction of a more direct route between the lowerstructure and the semiconductor pattern, thereby minimizing electricalresistance of an electric current path of a three-dimensionalsemiconductor device.

Example embodiments have been disclosed herein, and although specificterms are employed, they are used and are to be interpreted in a genericand descriptive sense only and not for purpose of limitation. In someinstances, as would be apparent to one of ordinary skill in the art asof the filing of the present application, features, characteristics,and/or elements described in connection with a particular embodiment maybe used singly or in combination with features, characteristics, and/orelements described in connection with other embodiments unless otherwisespecifically indicated. Accordingly, it will be understood by those ofskill in the art that various changes in form and details may be madewithout departing from the spirit and scope of the present invention asset forth in the following claims.

1-22. (canceled)
 23. A method of fabricating a three-dimensionalsemiconductor device, the method comprising: forming an upper structureon a lower structure, the upper structure including conductive patterns;forming a semiconductor pattern connected to the lower structure throughthe upper structure; and forming an insulating spacer between thesemiconductor pattern and the upper structure, such that a bottomsurface of the insulating spacer is positioned at a vertical levelequivalent to or higher than an uppermost surface of the lowerstructure.
 24. The method as claimed in claim 23, wherein: forming theupper structure on the lower structure includes forming a layer stack onthe lower structure, forming the insulating spacer includes: forming aninsulating layer vertically inserted into the layer stack, and etching alower region of the insulating layer to form the insulating spacer, suchthat the insulating spacer exposes a lower sidewall of the layer stack,and forming the semiconductor pattern includes forming the semiconductorpattern in the insulating spacer, such that the semiconductor pattern isdirectly connected to the lower structure through the layer stack. 25.The method as claimed in claim 24, wherein forming the insulating layerincludes: forming an opening through the layer stack to expose the lowerstructure; and forming the insulating layer on an inner wall of theopening.
 26. The method as claimed in claim 24, wherein: forming thelayer stack includes forming a plurality of horizontal layerssequentially deposited on the lower structure, and forming theinsulating layer includes: forming an opening in the layer stack, andforming the insulating layer on an inner wall of the opening, such thatthe opening is spaced apart from the lower structure, and such that atleast one of the horizontal layers remains between a bottom surface ofthe opening and the lower structure.
 27. The method as claimed in claim26, wherein forming the semiconductor pattern further comprises etchingthe horizontal layer remaining below the opening to expose the lowerstructure.
 28. The method as claimed in claim 26, wherein forming one ofthe horizontal layers includes forming a layer of aluminum oxide as anetch stop layer during formation of the opening.
 29. The method asclaimed in claim 24, wherein forming the layer stack includes formingalternating first horizontal layers and second horizontal layers on thelower structure, the first horizontal layers being formed of siliconoxide, and the second horizontal layers being formed of a materialhaving an etch selectivity with respect to the first horizontal layers.30. The method as claimed in claim 29, wherein forming the layer stackincludes forming one of the first horizontal layers as a lowermostlayer.
 31. The method as claimed in claim 29, wherein forming the layerstack includes forming one of the second horizontal layers as alowermost layer.
 32. The method as claimed in claim 29, furthercomprising, after forming the semiconductor pattern: removing the secondhorizontal layers to form recess regions exposing a sidewall of theinsulating spacer between the first horizontal layers; and formingconductive patterns in the recess regions.
 33. The method as claimed inclaim 32, further comprising, before forming the conductive patterns,forming an intermediate pattern in the recess region, such that theintermediate pattern and the insulating spacer define a memory layer.34. The method as claimed in claim 32, further comprising, beforeforming the conductive patterns: etching the exposed insulating spacerto expose a sidewall of the semiconductor pattern; and forming anintermediate pattern to cover the exposed sidewall of the semiconductorpattern, such that the insulating spacer remains in regions localizedbetween the semiconductor pattern and the first horizontal layers. 35.The method as claimed in claim 34, wherein forming the insulating spacerincludes forming a layer of at least one material having an etchselectivity with respect to the second horizontal layer.
 36. The methodas claimed in claim 24, wherein forming the semiconductor patternincludes: forming a semiconductor spacer to penetrate the insulatingspacer; and forming a semiconductor core directly connected to the lowerstructure through the semiconductor spacer.
 37. The method as claimed inclaim 36, further comprising, during formation of the insulating spacer,using the semiconductor spacer as an etch mask exposing the lower regionof the insulating layer.
 38. The method as claimed in claim 23, whereinforming the insulating spacer includes exposing the lower structurethrough an insulating layer, and forming the semiconductor patternincludes forming a semiconductor core to cover an inner sidewall of theinsulating spacer and the exposed lower structure.
 39. The method asclaimed in claim 23, wherein forming the lower structure includesforming a semiconductor substrate, such that the semiconductor patternis directly connected to the semiconductor substrate.
 40. The method asclaimed in claim 39, wherein forming the semiconductor substrateincludes: forming a doped region apart from the semiconductor pattern,the doped region having a different conductivity type from thesemiconductor pattern; and forming a connection region directlyconnected to the semiconductor pattern, the connection region having thesame conductivity type as the semiconductor pattern.
 41. The method asclaimed in claim 23, wherein forming the lower structure includesforming a substrate and a selection transistor interposed between thesubstrate and the upper structure, the selection transistor including aselection semiconductor pattern directly connected to the semiconductorpattern, and the bottom surface of the insulating spacer beingpositioned at a vertical level higher than the uppermost top surface ofthe selection semiconductor pattern.
 42. The method as claimed in claim23, wherein forming the lower structure includes formingthree-dimensionally arranged lower memory devices and a pad patterninterposed between the lower memory devices and the semiconductorpattern, the bottom surface of the insulating spacer being positioned ata vertical level higher than the uppermost top surface of the padpattern.